Conventionally, radiographic image detection devices, in which as a member to acquire a medical radiographic image, a solid-state imaging element referred to as a so-called flat panel detector (FPD) is two-dimensionally arranged, have been known. It is known that such radiographic image detection devices include direct-type devices in which using a photoconductive material such as a-Se (amorphous selenium) as a radiation detection element, radiation energy is directly converted into a charge and then this charge is read out as an electric signal in a pixel unit by a switching element for signal readout such as a two-dimensionally arranged TFT (Thin Film Transistor); and indirect-type devices in which radiation energy is converted into light using a scintillator and then this light is converted into a charge by a photoelectric conversion element such as a two-dimensionally arranged photodiode to be read out as an electric signal using a TFT.
And, over recent years, cassette-type radiographic image detection devices configured to be drivable with no cable and portable in which a battery is incorporated in the interior have been developed (for example, refer to Patent Document 1 and Patent Document 2). In the case where such a configuration is made for a radiographic image detection device, image capturing with a high degree of freedom including portable image capturing on the bed side of the patient can be carried out.
Conventionally, as a type in which a battery is charged, there has been used a type in which on the charging path, a charging circuit is provided and electric power having been fed from the outside is converted into electric power for battery charging to charge a battery (a first type); or a type in which electric power for battery charging is directly fed from the outside to charge a battery (a second type).
In the case of the first type, when electric power is fed from the outside, the voltage of the fed electric power is allowed to be high and the current value thereof is allowed to be low, and thereby conversion into appropriate voltage and current for a battery to be charged in the charging circuit of the interior can be carried out. In the case of employing this method, the current value needs not to be increased, and thereby when charging is carried out using a power feeding cable, the diameter of the power feeding cable needs not to be increased. Thereby, the power feeding cable does not stand in the way of image capturing even with charging, resulting in excellent manageability and operability.
On the other hand, in the case of the second type, since no power conversion is carried out inside a radiographic image detection device, just a small loss results, and thereby heat generation in the device interior can be inhibited. Further, quick charging with high current can be carried out.